The present invention relates generally to treatment of atrial fibrillation, as distinguished from ventricular defibrillation, by discharge of electrical energy in the region of the heart to convert atrial fibrillation into sinus rhythm, and more particularly to temporary monitoring and treatment of atrial rhythm disorders using an external defibrillator in conjunction with a temporary or permanent implanted catheter.
Longer life expectancy has brought with it significantly greater incidence of atrial fibrillation in the industrial nations. Atrial fibrillation is a primary cause of hospitalization for cardiac rhythm disorders in the United States, and an underlying cause of events of cerebrovascular stroke. Proper and timely treatment of atrial fibrillation for conversion to normal sinus rhythm would therefore go far to enhance expectancy and quality of life, and to reduce hemodynamic and thromboembolic complications. The use of anti-arrhythmic drugs has not been highly effective to reduce the incidence of atrial fibrillation, and has had undesirable side effects.
Application of external shocks with energies of between 100 and 350 joules is one therapy for treating atrial fibrillation, but it, too, has a number of risks and complications. Among them are late ventricular fibrillation, pericarditis attributable to the high electrical current, and spinal and other skeletal fractures arising from severe muscular contractions during application of the high energy shock(s).
The art of implanted atrial defibrillation electrodes using lower energies is well developed, as indicated for example by the disclosure of U.S. Pat. No. 5,282,837 dated Feb. 1, 1994 to J. Adams et al. The '837 patent describes the discharge of defibrillating energy from an implanted defibrillator, between two electrodes of an implanted catheter threaded through the coronary sinus. Energy discharge electrodes of the catheter are positioned beneath the left atrium near the left ventricle and in a region adjacent the right atrium coronary sinus ostium to minimize the potential for ventricular fibrillation. The implanted defibrillator senses arrhythmia and controls the energy discharge.
Ventricular fibrillation is also arrested with implanted systems as disclosed by Shulte et al in U.S. Pat. No. 5,269,319. In the '319 patent disclosure, two defibrillation electrodes on a single catheter are inserted via the superior vena cava into the right atrium and right ventricular cavity respectively. R-waves are detected and defibrillation impulse energy is synchronized therewith.
It is a general aim of the present invention to provide improved treatment of atrial fibrillation on a temporary basis, and to correct the deficiencies of the prior art.
A further aim of the invention is to significantly reduce the amount of energy required for treatment of atrial fibrillation from external impulse generators, by means of a hybrid system of internal defibrillating electrodes powered by external energy and control means.
Additional problems exist with necessity to implant prior art electrodes and to deliver sufficient energy for defibrillation. It is questionable whether the installation and operation of an implanted system is worthwhile for treating atrial fibrillation, which occurs only rarely. Effective prior art electrodes have large electrode surface areas to handle the high energy impulses, and are thus generally intrusive when implanted. Also, implantation of netting, barbs and anchors in the region of the heart presents a number of problems for which a solution has not been feasible to address a temporary system.
Conditions such as the potential for congestive heart failure can require continuous monitoring after defibrillation rather than or in addition to mere isolated shock treatment. Furthermore, cardiac surgery may call for post-operative monitoring for atrial dysrhythmias, and the delivery of instantaneous treatment when atrial fibrillation is detected.
Accordingly, it is a further object of the invention to provide a method and associated instrumentation for temporary use for limited periods of time to continuously monitor and instantaneously treat dysrhythmias and atrial fibrillation with adequate electrical field gradient shock energy, and without implantation other than temporarily for a catheter.